Hydrogen accumulation is a major concern in various industrial applications and processes. Hydrogen gas is highly flammable and is often generated or evolved as a by-product or waste emission. A hydrogen explosion can take place if the hydrogen concentration is allowed to exceed four (4%) percent. Furthermore, accumulations of hydrogen gas can present over-pressurization problems in sealed containers along with the attendant hazards of explosion and fire.
For instance, in U.S. Pat. No. 5,660,587 to Baer, which is incorporated herein by reference, a passive ventilation system and method for venting hydrogen from a chamber housing a battery is shown. As described in Baer, battery charging in remote cabinets, office building and electric vehicles has resulted in numerous explosions that destroy the battery and its container and possibly injure people. These explosions are frequently caused by igniting hydrogen gas in insufficiently ventilated battery chambers.
When batteries are overcharged, the current in the cell produces hydrogen. To avoid the accumulation of hydrogen in the battery, battery chambers are typically vented to release the hydrogen to the environment. The invention of Baer is directed to allow ventilation only when there is an increase of hydrogen concentration in the battery chamber. The invention however, does not address the removal of hydrogen from the environment to which it is vented.
As discussed in U.S. Pat. No. 5,624,598 to Shepodd, the operating life of a lamp, either incandescent or pressurized discharge lamps, can be greatly affected by the presence of certain gases in the internal lamp atmosphere. Water vapor is particularly harmful. In an incandescent lamp, for example, the temperature of the tungsten coil is sufficient to decompose water vapor into hydrogen and oxygen. Removal of the hydrogen is key in prolonging the useful life of the lamp. Shepodd seeks to solve this problem by disclosing hydrogen getters which are useful only at elevated temperatures.
In the nuclear industry, there is often a need to store and ship waste consisting of Pu-238 and high activity fraction of Pu-239. However, as a result of radiolysis, hydrogen gas is generated. The evolved gas poses an over-pressurization concern during storage, transportation and the ultimate disposal of the waste. Presently, waste consisting of Pu-238 and high activity fraction of Pu-239 cannot be shipped to long term storage areas, because of the hydrogen gas pressurization concerns of the storage containers. Thus, there remains a need in the industry for a method and container for reducing the concentration of hydrogen gas in a waste container consisting of Pu-238 and high activity fraction of Pu-239.
Various metals and metal alloys can absorb and then desorb large amounts of hydrogen under appropriate temperature and pressure conditions. These materials are referred to as metal hydrides and are well known in the art. They include pure metals such as Mg, Pd, Ti, Pt, U, and alloys such as those based on nickel, lanthanum and aluminum.
U.S. patent application Ser. No. 09/094,293, filed on Jun. 9, 1998 by the Applicant, and incorporated herein by reference, discloses a sol made from tetraethyl orthosiliate, ethanol, water and hydrochloric acid mixed with a hydrogen-absorbing metal alloy and solidified to form a porous glass matrix with the hydrogen absorbing alloy dispersed uniformly throughout the matrix to form a composite useful in the present invention. The composite is aged and subsequently heat treated to obtain a porosity that allows the hydrogen to react with the metal alloy to form a metal hydride, excluding poisonous CO and H.sub.2 S from the metal alloy. The metal alloy encapsulated in the porous matrix is, thus, protected from the hydride poisons present in the environment, e.g. a gaseous stream.
The composition used in the present invention is immune to gaseous poisons and is ideally suited for hydrogen absorption from environments where mixtures of various gases may be present.